It is known that the tight joining of two metal pipes can often raise difficulties, particularly if the joining means used are required to be as light as possible and quick-fittable. This is especially the case in the motor-vehicle industry, when the object is to produce an engine exhaust pipe with several sections of metal pipes.
It has already been proposed to this effect, for example in U.S. Pat. No. 3,964,773, to shape the facing ends of the pipes to be joined in such a way that they present complementary bearing surfaces of generally conical shape. A clamp is then placed around such conical surfaces which project with respect to the pipes outer surface, in order to hold them one against the other, thereby ensuring a tight connection as well as the necessary mechanical rigidity.
Such a clamp comprises two semi-circular elements of inverted V-shaped cross-section, adapted to fit over the projecting conical surfaces of the pipes.
Each semi-circular element is provided at its ends with flanges, which flanges are adapted to be assembled together by way of screws or bolts. In the case of the aforesaid U.S. patent, the semi-circular elements are provided at one of their ends with articulated joining means permitting the use of only one bolt for tightening the clamp.
This type of clamp takes a relatively long time to be fitted as it often requires the assembling and tightening of at least two bolts. Also, the tightening forces are unevenly used, and in particular, unevenly distributed, as they tend to bring closer together the two relatively rigid semi-circular elements, without exerting an even tension around their periphery.
French Pat. No. 3,91 031 767 has proposed the tight connecting of large diameter ventilation pipes by using an arrangement and a clamp similar to those described hereinabove. It is however noted that this patent requires the use of "reinforcing flanges" arranged in straddling fashion on the conical ends of the pipes to be joined, this making it virtually impossible to apply the teaching of said patent to joining pipes intended to constitute the exhaust system of a motor-vehicle.
It should finally be noted that the devices and arrangements briefly described in the foregoing generally require a seal, of rubber or similar material, interposed between the complementary bearing surfaces of the pipes. The presence of such a seal obviously complicates the operation of joining pipes, especially at the mass production level; there is also a source of inconvenience arising from the risks of the seal being damaed by hot and corrosive gases.